1. Field of the Invention
The present invention relates to a non-magnetic one-constituent type developing agent, and more particularly an electro-photographic developing agent characterized by providing high quality images without fogging, scattering of toners and ineffective development by maintaining a stable charge and charge distribution of a toner over an extended lifetime in a developing apparatus of an electro-photographic image processing device. In addition, the developing agent has deodorizing, anti-bacterial and sterilizing functions.
2. Description of the Related Art
Electro-photographic image processing devices such as laser printers, facsimiles, copying machines, and the like are now widely used. These devices form desired images by forming latent images on photoreceptors by employing lasers, moving toners onto the latent images on the photoreceptors by using an electric potential difference, and then transferring the images onto printing media, such as paper.
Conventionally, most electro-photographic image processing devices are black and white type with dry toners. These devices are actuated by injecting charges into toners by frictional charging, and then allowing toners to move into latent images on a photoreceptor (OPC) in response to an electric potential difference. Since this type of toner is in the form of powder, environmental problems may be caused due to particulates therein. However, the devices have simple manufacturing processes, and thus, are economical, and enable the miniaturization of image-processing devices.
In the field of electro-photographic image processing devices, the term “developing agent” usually refers to a state in which carriers are mixed with toners, and also to the toner itself when carriers are not used.
Dry developing agents are classified into one-constituent type developing agents and two-constituent type developing agents, depending on the type of the charging manner of the developing agent, and are classified into magnetic and non-magnetic developing agents depending on the manners for transferring charged toner particles to a latent image. The one-constituent type developing agent is charged through friction between toner particles or friction with sleeves, and the two-constituent type developing agent is charged through friction caused by mixing non-magnetic toners and magnetic carrier particles. The two-constituent type-developing agent may provide relatively stable and effective recording images and may be applied to high-speed development. However, deterioration of carriers or a change in the mixed ratio of the developing agent and the carrier readily occurs, and a device using the same is bulky. Thus, the one-constituent type-developing agent is generally used in smaller devices, is low cost, has high reliability, and the like. The non-magnetic developing agent is moved by the mobility of the developing agent itself without the use of a magnetic force, and the magnetic developing agent may be moved by mixing magnetic materials, such as ferrite, into the developing agent. The non-magnetic developing agent is inexpensive since it does not contain magnetized particles and may be used for color printing.
A low temperature fusing property of toners reduces the energy consumption, the printing waiting time, and the like, of the printing devices, and a release agent (wax) and a binder resin having a wide range of superior fusing properties are used for this purpose. Furthermore, for a non-magnetic one-constituent polymerizing or pulverizing toner, improvements in the mobility and the charge properties of the toner particles have been achieved by forming a sphere of particles and externally adding silica, TiO2, and the like, to the sphere of particles to enhance a developing property, durability, transferring efficiency, and anti-fogging of a non-imaging part.
When using a non-contacting non-magnetic one-constituent developing method, the apparatus may be miniaturized, color corresponding is facilitated, and an edge reproduction and a tone gradation are sufficient for producing high-resolution images. However, in a non-contacting non-magnetic one-constituent developing method, a constant charge quantity and a uniform distribution of a toner must be maintained both after long periods of image printing, as well as in the initial stage of image printing, to maintain a stable developing property, and to prevent fogging and scattering, and the like. To provide the uniform charge to a toner, a uniform thin toner layer has to be formed on a developing roller. However, thinning of the toner layer causes stress in the toner, thus causing deterioration of the toner. Also, the toner layer is fused to the control blade, thus causing streaks easily. In forming a thin layer of a toner on a developing roller, a significant decrease in development efficiency and a decrease in image density may readily occur due to an increase in toner charges, and when the toner charges are decreased to improve the decrease in development efficiency, an increase in fogging and contamination by scattering, and the like, may occur.
That is, it is important to maintain a superior developing property without fog even after an extended period of image printing in the non-contacting non-magnetic one-constituent developing method, and to do this, a stable charge quantity and a uniform charge distribution in a toner must be maintained during image printing.
To achieve this, and for the purpose of removing materials having ineffective electric resistance, such as residual toner or paper powder, or an ozone adduct stuck to a photoreceptor and a control blade, 2 or 3 classes of inorganic particulates, in addition to silica, are added to the toner and mixed. The inorganic particulates provide a cleaning effect as a grinding agent, but do not satisfactorily enhance a toner-transferring property.
The developing toner used in an electro-photographic image forming apparatus comprises the constituent material of the toner itself, impurities generated in a manufacturing process, and minute amounts of coloring materials, in particular, low molecular weight coloring materials, into which a portion of the toner constituents decomposes in a storage environment after being manufactured. Such materials may cause discomfort due to irritant odors when using the toner and opening the toner container (cartridge). A heat fusing process for fusing a toner onto a printing medium, such as paper, may cause discomfort to a user since the printed image is heated, and minute constituents included in the toner enter the atmosphere. To reduce the amount of minute constituents released into the atmosphere, the main body of the apparatus may be equipped with a filter to adsorb ozone, odor, and the like. However, use of a filter increases production costs and causes annoyance due to its need to be changed regularly.
Furthermore, careful attention must be paid to the storage environment of the dry toner of an image forming apparatus since treatment such as sterilization of the toner and its container (cartridge) is not carried out. For long-term storage, bacteria, fungi, and the like, proliferate inside the toner container, which may adversely affect the quality of a printed image and harm the user. Particularly, after an image is formed on a printing medium, such as paper, many users contact the resulting images, but little attention is given to this. That is, attention and precaution are required for storage of the toner for the image forming apparatus and for the proliferation of bacteria, fungi, and the like, after an image is formed on the printing medium (e.g., paper or the like) because of the proliferation of bacteria, fungi, and the like.
Japanese laid-open patent application No. 8-314179 discloses a dry toner in which a metal ion having anti-bacterial activity is incorporated. The metal ion is incorporated into aluminosilicate, and then the aluminosilicate is incorporated into the toner. This manner of incorporating metal ions appears to use metal ions to avoid the technical difficulty of producing a particle metal, and to decrease costs. Also, the treatment in a liquid state is necessary to incorporate the metal ion into the toner. However, a difficult process is required to do this, and thus, the metal ions are incorporated into the aluminosilicate and the aluminosilicate is incorporated into the toner.
A general image forming process comprises: a charging process in which a constant charge is imparted to a photoreceptor composed of a photoconductive material; a photo-exposing process in which a latent image is formed on a photoreceptor using a laser; a developing process in which a toner image is formed by developing a developing agent on the latent image on the photoreceptor; a transferring process in which the toner image is transferred to a transfer material such as paper; a fusing process in which the toner transferred to the transfer material is fused using heat or pressure; and a cleaning process in which toners and residues remaining on a carrier of the latent image are cleaned. By repeating these respective processes, desired copies or printed products are obtained. Developing processes are classified into a contacting-type and a non contacting-type. In a contacting-type developing process, a developing agent is developed on the latent image by contacting a developing roller with a surface of a photoreceptor, and in a non contacting-type developing process, the developing roller and the surface of the photoreceptor are separated, and the developing agent is moved by electrical forces generated by an electrical potential difference between the developing roller and the photoreceptor. The contacting-type developing process is disadvantageous because the photoreceptor and the developing roller wear away, while the non contacting-type developing process is advantageous because the durability of the apparatus is more effective and the resolution is more effective since an image is developed using electrical forces.
The mobility and electrical properties of dry developing agents must not change over time or in different environmental conditions (e.g., temperature and humidity). Particularly, the developing agent of a conventional non-magnetic one-constituent developing apparatus obtains charge characteristics through frictional charging with a developing carrier, a control blade of a developing agent and a developing agent providing member. However, as a printing process is repeated, the external additives of the developing agent become embedded in the resin of the developing agent due to stress, or are separated from the developing agent. If this occurs, the mobility of the developing agent decreases, and the physical adsorptions among the developing carrier, the control blade of the developing agent and the developing agent increase. Thus, uniform frictional charging of the developing agent does not occur and the desired frictional charging property of the developing agent deteriorates. As a result, the developing agent does not become charged or its polarity becomes changed into counter polarity, and this uncharged developing agent or a developing agent having counter polarity is developed on a non-image area, causing image contamination such as fog to occur. Increasing the amount of external additives to prevent such problems causes an increase in the amount of frictional charge of the developing agent and an increase in the force between the developing agent and the developing carrier. Thus, the amount of the toner moved to the photoreceptor decreases, causing a decrease in the developing efficiency and the image density.
Also, as the amount of external additives is increased, the cleaning property of the cleaning blade which removes the remaining developing agent deteriorates, and thus, the charging roller is contaminated, and the remaining developing agent or impurity remains on the carrier of the latent image, causing the generation of spots in the image, and/or vertical white line/black lines, thus deteriorating the image quality.